refactor(project): remove support for jest

[joshblack]

Closes https://github.com/github/primer/issues/5336

Removes Jest from the project in favor of Vitest now that our migration is complete 🫡

Changelog

New

Changed

• Update vitest to be the default test runner
• Update references to Jest to instead point to Vitest

Removed

• Remove support for Jest from the project
• Remove vitest migration from our migration tracking workflow

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4d6a499

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[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	90.12 KB (0%)
packages/react/dist/browser.umd.js	90.43 KB (0%)

[Copilot]

Pull Request Overview

This PR completes the migration from Jest to Vitest as the default test runner for the Primer React project. The key changes focus on removing Jest-specific dependencies, configuration files, and updating test files to use Vitest APIs.

• Remove Jest configuration files and dependencies
• Update test files to use Vitest imports and APIs instead of Jest
• Clean up migration tracking workflow and scripts
• Update documentation to reference Vitest instead of Jest

Reviewed Changes

Copilot reviewed 23 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/ToggleSwitch/__snapshots__/ToggleSwitch.test.tsx.snap	Remove Jest snapshot file (entire file deleted)
script/vitest-migration-status.mts	Remove migration tracking script (entire file deleted)
packages/react/vitest.config.browser.mts	Simplify test inclusion patterns and add exclusions
packages/react/src/utils/testing.tsx	Remove Jest-specific testing utilities (entire file deleted)
packages/react/src/utils/test-matchers.tsx	Remove Jest-specific test matchers (entire file deleted)
packages/react/src/utils/test-helpers.tsx	Add TypeScript suppression comment
packages/react/src/utils/test-deprecations.tsx	Remove Jest-specific deprecation handling (entire file deleted)
packages/react/src/experimental/UnderlinePanels/UnderlinePanels.test.tsx	Update to use Vitest imports and mock functions
packages/react/src/__tests__/BaseStyles.test.tsx	Add type assertions for style expectations
packages/react/src/Overlay/Overlay.test.tsx	Fix style assertion value types
packages/react/src/Dialog/Dialog.test.tsx	Remove Jest-specific matchmedia mock setup
packages/react/src/DataTable/__tests__/DataTable.test.tsx	Add type assertion for style expectation
packages/react/src/ActionList/ActionList.test.tsx	Remove axe accessibility test and unused imports
packages/react/package.json	Remove Jest-related dependencies
packages/react/jest.config.js	Remove Jest configuration file (entire file deleted)
packages/postcss-preset-primer/package.json	Remove Babel and Jest dependencies
packages/postcss-preset-primer/config/transform/jsTransform.js	Remove Babel Jest transformer (entire file deleted)
package.json	Update root package.json to use Vitest commands and remove Jest dependencies
eslint.config.mjs	Remove Jest ESLint plugin configuration
contributor-docs/testing.md	Update documentation to reference Vitest instead of Jest
contributor-docs/CONTRIBUTING.md	Update technology stack reference from Jest to Vitest
.github/workflows/migration-status.yml	Remove Vitest migration tracking workflow
.github/workflows/ci.yml	Update CI workflow to use single test command

[Copilot]

The @ts-nocheck directive suppresses all TypeScript checking for this file. This is generally discouraged as it bypasses type safety. Consider either fixing the TypeScript issues or using more specific suppressions like @ts-expect-error or @ts-ignore for individual problematic lines.

Suggested change

	// JSDOM doesn't mock ResizeObserver
	import {TextEncoder} from 'node:util'
	// JSDOM doesn't mock ResizeObserver
	// @ts-expect-error: ResizeObserver is not defined in Node.js global types

[Copilot]

The mock implementation for console.error should use a named function or store the original implementation to restore it properly. Consider using mockImplementation(vi.fn()) or storing the original function for better test isolation.

Suggested change

	const spy = vi.spyOn(console, 'error').mockImplementation(() => {})
	const spy = vi.spyOn(console, 'error').mockImplementation(vi.fn())

[jonrohan]

Heck yea!